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Lets talk wheels

Roost hubs and carbon rims

Let’s talk wheels

Upgrading your wheels can have a big impact on the way your bike rides.

Buying a new pair of mountain bike wheels is a sizeable investment, but choose wisely and it can actually be the most transformative upgrade to your riding experience that you can make.

On the surface, wheels simply roll and support tyres that cushion the bike from the terrain.

Dig deeper though, and different products all transfer power variably, accelerate at a range of rates and conform to bumps uniquely. Freehub and hub designs impact durability, serviceability and rolling resistance, while every rim responds differently to impacts. There’s a lot to take in.

Carbon-fibre rims are often thought of as the ultimate wheel upgrade, but high-end extruded aluminium rims can be just as light and offer an even more forgiving ride – in fact many top enduro racers still bank on alloy rims instead of carbon.

Both materials have advantages, but the general consensus is that carbon ‘should’ produce a tougher and rounder wheel, although the flipside of this is that they can fail catastrophically, while an alloy rim may be temporarily repairable – enough to get you home. Our experience is that modern carbon rims rarely break, while alloy rims can ding or dent relatively easily which can cause tubeless tyres to leak air and lose their seal.

Overall, it’s hard to draw general conclusions about either material – as ever, it comes down to the design and construction of specific products.

If you’re going to the trouble and expense of upgrading though, your new hoops better improve performance or what’s the point, right? The after-market wheel sets should noticeably improve rolling speed, handling, and acceleration over cheaper, stock wheels, and if you shop wisely you can have the best of both worlds, balancing fast and zingy against strength and comfort.

The popularity of longer-travel enduro bikes and faster and more technical tracks means wheels get abused more than ever. This partly explains the sector’s bias towards strength and toughness over weight saving and maximum efficiency. Weight is still a crucial factor, however, in terms of rolling speed, acceleration and less rotating mass to drag uphill and we’re frequently surprised by wheel tests downplaying this aspect.

Nowadays there is a plethora of great wheels to choose from; the set that best suits your needs will depend on the compromise between cost and performance that matters most for your riding style and terrain.

Weight

Lighter wheels accelerate and slow down faster, change direction quicker and make climbing easier. It’s not always that simple though, as wheel roundness and stiffness are factors too, plus the physics involved with rotating mass and centrifugal forces means weight closer to the outside edge makes more difference, so a heavier wheel with a proportionally lighter rim can still spin up to speed faster.

Spoke count and design

Extra spokes add strength, but also weight, and can reduce comfort in terms of bump swallowing. They can also improve resistance to twisting or lateral flex, increase overall strength and durability and should ensure a wheel stays tighter and truer longer too. Any spokes chosen have to match budget constraints and can use different gauges, buttings (thicker and thinner zones to save weight) and profiles to tune ride quality. Proprietary spokes are often harder to replace and source.

Rim width

Most modern rims have become wider. The extra room inside allows the sidewalls of broader, grippier and more comfortable tyres to sit naturally and inflate as manufacturers intended. Rim material, shape and depth also have a marked influence on impact strength, stiffness and compliance. Plenty new tubeless rims forego a bead hook to save weight and boost sidewall resilience, and it’s now accepted tubeless tyres mount, stay inflated and remain stable with a multitude of quirky rim profiles.

Bearings and sealing

How smoothly (and ultimately how fast) wheels spin is closely linked to bearing quality and design. Riders that live in wet areas where grit and crud can get inside hubs and eat into a precious investment are looking for good seal protection. Balls and bearing casing specification, rubber seals, and grease all effect lifespan, but better sealing can also add friction, which reduces rolling speed. Beware special bearing sizes and fiddly designs that are a faff to service too. Cup and cone (open) bearings are still common in Shimano hubs and spin well, but require more looking after.

Engagement or pick up

Most hub designs use a pawl system of some description whereby small metal ‘hooks’ engage into a ratchet to drive the hub, then disengage to allow the hub to freewheel. Different designs have their own levels of drag (resistance to spinning freely) while not pedalling and engagement (measured in degrees of rotation). A faster pick up means power is delivered quicker; especially useful for technical climbing where lower gears and higher torques mean responsiveness is key. Faster engagement can eat into durability and strength, since splines or ratchet teeth first need to be smaller to be closer enough together to enable it.

The Roost Nero and Otho carbon rims have been designed for Enduro and XC riding respectively. The Nero carbon rims are very tough and have a high strength rating and wide profile. The Otho carbon rims are lighter and offer both a 25mm and 30mm internal diameter. Pair these with our Roost high engagement hub sets and you’ll have a winning set of wheels that will be fast, snappy, tough and light weight.

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